Many building materials, and particularly those that are comprised largely of inorganic compounds, such as masonry, cement, brick, concrete, and the like, are naturally porous. Thus, these building materials possess capillary networks that allow water to penetrate and evaporate from the building material, as well as migrate through the building material.
It is common practice to build structures wherein units of building material are placed adjacent to one another, with the expectation that the two units will form a strong bond. Placing bricks into a Portland cement-based bonding agent, such as mortar, is one example. While the strength of such a bond will depend on several factors, one important factor is the relative suction of the two building materials. In essence, "suction" refers to the tendency of a building material to draw moisture from, or release moisture to, a neighboring structure. Suction may also be referred to as the degree of water absorption exhibited by a material.
The use of bricks and mortar to form a wall provides one illustration of the importance of suction. Brick is typically formed in a kiln, and is quite dry upon leaving the kiln. However, upon sitting under ambient conditions, bricks may absorb some moisture from the air, in an amount depending on ambient temperature and humidity. On the other hand, mortar is quite wet in the uncured state which is used to join bricks together. When brick and uncured mortar come into contact, moisture from the mortar will migrate into the adjacent brick. If the brick exhibits high suction, moisture will migrate rapidly and to a large extent from the mortar into the brick. However, mortar has an optimum curing rate and water content in order for the mortar to fully hydrate and form a strong, non-crumbling structure. Rapid and/or large loss of moisture from the mortar can lower the internal strength of the mortar, as well as the strength of the bond that forms between the brick and the mortar.
In theory, compensation for undesirable suction may be achieved by adjusting the water content of building materials. For example, extra water may be added to grouts, mortars, and other cementitious materials to compensate for the amount that will be absorbed by the brick. Another approach that is sometimes taken is to "pre-wet" the brick, that is, dip the brick in water or spray water on the brick, so that it will display reduced suction. However, in practice, it is very difficult to determine how much extra water should be added to grout or brick, and it is typically the case that the desired bond strength is not obtained by these approaches.
The moisture content of building materials, and the degree and rate at which moisture moves through and/or evaporates from building materials, has implications beyond an effect on bond strengths. For example, excess moisture within porous building materials is a serious problem to the industry. Freeze--thaw cycles create alternate expansion and contraction of the porous building materials that can lead to spalling and disintegration. Biological growth of microbes, mosses, lichens and the like also cause damage and are an aesthetic detriment. Porous building materials that are damp have a decreased R - value and thereby cause heat loss in winter and overheating in summer. Movement of moisture through building materials can cause concomitant salt migration to the surface of building material, thus giving rise to efflorescence.
Accordingly, there is a need in the art for a method to treat building materials in order to affect the moisture content of the building material, and to affect the rate and extent to which moisture migrates into, through and out of building material. The present invention solves these long-standing needs, and provides other related advantages, as discussed below.